Abstract: An arrangement for mounting a heat sink to a mounting board. The arrangement includes a heat sink and a locking member. The heat sink has a bottom surface and a passageway extending therein from an entrance opening on the bottom surface in a direction normal thereto and terminating with a closed end at its inner end. The passageway has an entrance region tapering toward the closed end and an inner region defined by generally parallel side wall portions. The side wall portions defining the entrance region including an engagement surface facing the closed end of the passageway. The locking member is T-shaped with the member crossing the stem of the T adapted for snug fit engagement with the generally parallel walls of the passageway's inner region. Moreover, the crossing member has an engagement member at each of it's ends that extend toward the base of the stem. The engagement members interlock with the engagement surface when the locking member is inserted into the passageway of the heat sink.